Mailing machines are of course in common use for applying postage to envelopes. Such machines now typically employ a thermal ink ribbon, comprised of a thin plastic film coated with a fusible layer comprising an ink composition, which composition is transferred, in selected patterns for printing postage and graphics, to an envelope passed in contact therewith under a thermal print head of the machine.
U.S. Pat. No. 5,959,652 provides a concise description of such a mailing machine and a thermal ink ribbon cassette suitable for use therein. The disclosure of that patent, at lines 13 through 49 in column 1 and at line 32 of column 5 to line 58 of column 6, together with FIG. 1, is hereby incorporated here-into by reference thereto. The following U.S. Pat. Nos. are also of interest to the present invention: 4,908,632; 5,192,149; 5,392,148; 5,529,410; 5,619,244; 5,917,532; 5,933,179; and 6,301,522.
Despite the extensive efforts that have been devoted to the development of thermal ink ribbon cassettes for mailing machines, of which the foregoing prior art is indicative, improvements in the design and construction of such cassettes would of course be desirable. In particular, although the need for establishing and maintaining a proper tension upon the ink ribbon has been well recognized and addressed, it is not believed that optimal means for doing so has heretofore been provided. Moreover, while suitable anti-reverse mechanisms are known for preventing unwinding of the used ribbon from the take-up spindle, in their present forms such mechanisms tend to be unduly complex, not entirely effective, or both.